TextCheck

Run-on sentence checker

Find fused sentences, comma splices and sentences that run far too long, then split them where it reads naturally.

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Three kinds of run-on

  • Fused sentence: two sentences with no punctuation between them. “I love to write I do it every day.”
  • Comma splice: two sentences joined only by a comma. “I love to write, I do it every day.”
  • The long, breathless sentence: technically correct but so long that readers lose the thread. Anything past 30–35 words with few pauses deserves a second look.

Five ways to fix one

  • Full stop: “I love to write. I do it every day.”
  • Semicolon: “I love to write; I do it every day.”
  • Comma + conjunction (and, but, or, so, yet, for, nor): “I love to write, so I do it every day.”
  • Subordinate one clause: “Because I love to write, I do it every day.”
  • Cut and restructure: “I write every day because I love it.”

Is a long sentence a run-on?

Not necessarily. A run-on is about structure, not length: “I ran.” plus “She stayed.” fused together is a run-on at four words. But very long sentences are hard to read, so TextCheck marks them separately with a readability note rather than calling them errors.

Questions people ask

What is the difference between a run-on and a comma splice?

A comma splice is one type of run-on: two independent clauses joined with only a comma. A fused sentence has no punctuation at all between them.

How long is too long for a sentence?

Plain-language guidance, such as the UK Government Digital Service style guide, suggests aiming for 25 words or fewer on average. Longer sentences are fine occasionally for rhythm.

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